REST api added for asset transfer in Golang

Signed-off-by: Basil K Y <techiebasil@gmail.com>

asset-transfer-basic/rest-api-go/.gitignore

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+go.sum
+Requests.http
+rest-api-go

asset-transfer-basic/rest-api-go/README.md

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+# Asset Transfer REST API Sample
+
+This is a simple REST server written in golang with endpoints for chaincode invoke and query.
+
+  
+## Usage
+
+- Setup fabric test network and deploy the asset transfer chaincode by [following this instructions](https://hyperledger-fabric.readthedocs.io/en/release-2.4/test_network.html).
+
+- cd into rest-api-go directory
+- Download required dependencies using `go mod download`
+- Run `go run main.go` to run the REST server
+
+## Sending Requests
+
+Invoke endpoint accepts POST requests with chaincode function and arguments. Query endpoint accepts get requests with chaincode function and arguments.
+
+Sample chaincode invoke for the "createAsset" function. Response will contain transaction ID for a successful invoke.
+
+``` sh
+curl --request POST \
+  --url http://localhost:3000/invoke \
+  --header 'content-type: application/x-www-form-urlencoded' \
+  --data = \
+  --data channelid=mychannel \
+  --data chaincodeid=basic \
+  --data function=createAsset \
+  --data args=Asset123 \
+  --data args=yellow \
+  --data args=54 \
+  --data args=Tom \
+  --data args=13005
+```
+Sample chaincode query for getting asset details.
+
+``` sh
+curl --request GET \
+  --url 'http://localhost:3000/query?channelid=mychannel&chaincodeid=basic&function=ReadAsset&args=Asset123' 
+  ```

asset-transfer-basic/rest-api-go/go.mod

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+module rest-api-go
+
+go 1.19
+
+require (
+	github.com/hyperledger/fabric-gateway v1.1.0
+	google.golang.org/grpc v1.49.0
+)
+
+require (
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/hyperledger/fabric-protos-go-apiv2 v0.0.0-20220615102044-467be1c7b2e7 // indirect
+	github.com/miekg/pkcs11 v1.1.1 // indirect
+	golang.org/x/net v0.0.0-20220526153639-5463443f8c37 // indirect
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+	golang.org/x/text v0.3.7 // indirect
+	google.golang.org/genproto v0.0.0-20220527130721-00d5c0f3be58 // indirect
+	google.golang.org/protobuf v1.28.0 // indirect
+)

asset-transfer-basic/rest-api-go/main.go

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+package main
+
+import (
+	"fmt"
+	"rest-api-go/web"
+)
+
+func main() {
+	//Initialize setup for Org1
+	cryptoPath := "../../test-network/organizations/peerOrganizations/org1.example.com"
+	orgConfig := web.OrgSetup{
+		OrgName:      "Org1",
+		MSPID:        "Org1MSP",
+		CertPath:     cryptoPath + "/users/User1@org1.example.com/msp/signcerts/cert.pem",
+		KeyPath:      cryptoPath + "/users/User1@org1.example.com/msp/keystore/",
+		TLSCertPath:  cryptoPath + "/peers/peer0.org1.example.com/tls/ca.crt",
+		PeerEndpoint: "localhost:7051",
+		GatewayPeer:  "peer0.org1.example.com",
+	}
+
+	orgSetup, err := web.Initialize(orgConfig)
+	if err != nil {
+		fmt.Println("Error initializing setup for Org1: ", err)
+	}
+	web.Serve(web.OrgSetup(*orgSetup))
+}

asset-transfer-basic/rest-api-go/web/app.go

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+package web
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+)
+
+// OrgSetup contains organization's config to interact with the network.
+type OrgSetup struct {
+	OrgName      string
+	MSPID        string
+	CryptoPath   string
+	CertPath     string
+	KeyPath      string
+	TLSCertPath  string
+	PeerEndpoint string
+	GatewayPeer  string
+	Gateway      client.Gateway
+}
+
+// Serve starts http web server.
+func Serve(setups OrgSetup) {
+	http.HandleFunc("/query", setups.Query)
+	http.HandleFunc("/invoke", setups.Invoke)
+	fmt.Println("Listening (http://localhost:3000/)...")
+	if err := http.ListenAndServe(":3000", nil); err != nil {
+		fmt.Println(err)
+	}
+}

asset-transfer-basic/rest-api-go/web/initialize.go

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+package web
+
+import (
+	"crypto/x509"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"path"
+	"time"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+	"github.com/hyperledger/fabric-gateway/pkg/identity"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+// Initialize the setup for the organization.
+func Initialize(setup OrgSetup) (*OrgSetup, error) {
+	log.Printf("Initializing connection for %s...\n", setup.OrgName)
+	clientConnection := setup.newGrpcConnection()
+	id := setup.newIdentity()
+	sign := setup.newSign()
+
+	gateway, err := client.Connect(
+		id,
+		client.WithSign(sign),
+		client.WithClientConnection(clientConnection),
+		client.WithEvaluateTimeout(5*time.Second),
+		client.WithEndorseTimeout(15*time.Second),
+		client.WithSubmitTimeout(5*time.Second),
+		client.WithCommitStatusTimeout(1*time.Minute),
+	)
+	if err != nil {
+		panic(err)
+	}
+	setup.Gateway = *gateway
+	log.Println("Initialization complete")
+	return &setup, nil
+}
+
+// newGrpcConnection creates a gRPC connection to the Gateway server.
+func (setup OrgSetup) newGrpcConnection() *grpc.ClientConn {
+	certificate, err := loadCertificate(setup.TLSCertPath)
+	if err != nil {
+		panic(err)
+	}
+
+	certPool := x509.NewCertPool()
+	certPool.AddCert(certificate)
+	transportCredentials := credentials.NewClientTLSFromCert(certPool, setup.GatewayPeer)
+
+	connection, err := grpc.Dial(setup.PeerEndpoint, grpc.WithTransportCredentials(transportCredentials))
+	if err != nil {
+		panic(fmt.Errorf("failed to create gRPC connection: %w", err))
+	}
+
+	return connection
+}
+
+// newIdentity creates a client identity for this Gateway connection using an X.509 certificate.
+func (setup OrgSetup) newIdentity() *identity.X509Identity {
+	certificate, err := loadCertificate(setup.CertPath)
+	if err != nil {
+		panic(err)
+	}
+
+	id, err := identity.NewX509Identity(setup.MSPID, certificate)
+	if err != nil {
+		panic(err)
+	}
+
+	return id
+}
+
+// newSign creates a function that generates a digital signature from a message digest using a private key.
+func (setup OrgSetup) newSign() identity.Sign {
+	files, err := ioutil.ReadDir(setup.KeyPath)
+	if err != nil {
+		panic(fmt.Errorf("failed to read private key directory: %w", err))
+	}
+	privateKeyPEM, err := ioutil.ReadFile(path.Join(setup.KeyPath, files[0].Name()))
+
+	if err != nil {
+		panic(fmt.Errorf("failed to read private key file: %w", err))
+	}
+
+	privateKey, err := identity.PrivateKeyFromPEM(privateKeyPEM)
+	if err != nil {
+		panic(err)
+	}
+
+	sign, err := identity.NewPrivateKeySign(privateKey)
+	if err != nil {
+		panic(err)
+	}
+
+	return sign
+}
+
+func loadCertificate(filename string) (*x509.Certificate, error) {
+	certificatePEM, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read certificate file: %w", err)
+	}
+	return identity.CertificateFromPEM(certificatePEM)
+}

asset-transfer-basic/rest-api-go/web/invoke.go

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+package web
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/hyperledger/fabric-gateway/pkg/client"
+)
+
+// Invoke handles chaincode invoke requests.
+func (setup *OrgSetup) Invoke(w http.ResponseWriter, r *http.Request) {
+	fmt.Println("Received Invoke request")
+	if err := r.ParseForm(); err != nil {
+		fmt.Fprintf(w, "ParseForm() err: %s", err)
+		return
+	}
+	chainCodeName := r.FormValue("chaincodeid")
+	channelID := r.FormValue("channelid")
+	function := r.FormValue("function")
+	args := r.Form["args"]
+	fmt.Printf("channel: %s, chaincode: %s, function: %s, args: %s\n", channelID, chainCodeName, function, args)
+	network := setup.Gateway.GetNetwork(channelID)
+	contract := network.GetContract(chainCodeName)
+	txn_proposal, err := contract.NewProposal(function, client.WithArguments(args...))
+	if err != nil {
+		fmt.Fprintf(w, "Error creating txn proposal: %s", err)
+		return
+	}
+	txn_endorsed, err := txn_proposal.Endorse()
+	if err != nil {
+		fmt.Fprintf(w, "Error endorsing txn: %s", err)
+		return
+	}
+	txn_committed, err := txn_endorsed.Submit()
+	if err != nil {
+		fmt.Fprintf(w, "Error submitting transaction: %s", err)
+		return
+	}
+	fmt.Fprintf(w, "Transaction ID : %s Response: %s", txn_committed.TransactionID(), txn_endorsed.Result())
+}

asset-transfer-basic/rest-api-go/web/query.go

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+package web
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Query handles chaincode query requests.
+func (setup OrgSetup) Query(w http.ResponseWriter, r *http.Request) {
+	fmt.Println("Received Query request")
+	queryParams := r.URL.Query()
+	chainCodeName := queryParams.Get("chaincodeid")
+	channelID := queryParams.Get("channelid")
+	function := queryParams.Get("function")
+	args := r.URL.Query()["args"]
+	fmt.Printf("channel: %s, chaincode: %s, function: %s, args: %s\n", channelID, chainCodeName, function, args)
+	network := setup.Gateway.GetNetwork(channelID)
+	contract := network.GetContract(chainCodeName)
+	evaluateResponse, err := contract.EvaluateTransaction(function, args...)
+	if err != nil {
+		fmt.Fprintf(w, "Error: %s", err)
+		return
+	}
+	fmt.Fprintf(w, "Response: %s", evaluateResponse)
+}